//! Editor functionality
use crate::helpers::*;

use std::cmp::PartialEq;
use std::fs::File;
use std::io;
use std::io::prelude::*;
use std::io::BufReader;
use std::time::{Duration, Instant};

use self::EditorKey::*;

const KILO_TAB_STOP: usize = 4;
const KILO_QUIT_TIMES: u8 = 3;

/// A representation of a line in the editor
#[derive(Debug, Default)]
pub struct EditorRow {
    chars: String,
    render: String,
}

impl EditorRow {
    pub fn new(chars: &str) -> Self {
        let mut instance = EditorRow::default();
        instance.chars = chars.to_owned();

        instance
    }
}

/// Main structure for the editor
/// `EditorConfig` struct in C version
#[derive(Debug)]
pub struct Editor {
    cursor_x: usize,
    cursor_y: usize,
    render_x: usize,
    col_offset: usize,
    row_offset: usize,
    screen_cols: usize,
    screen_rows: usize,
    rows: Vec<EditorRow>,
    dirty: u64,
    filename: String,
    status_message: String,
    status_message_time: Instant,

    // Properties not present in C version
    output_buffer: String,
    quit_times: u8,
}

/// Keycode mapping enum
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum EditorKey<T> {
    Enter,
    Escape,
    Backspace,
    ArrowLeft,
    ArrowRight,
    ArrowUp,
    ArrowDown,
    DeleteKey,
    HomeKey,
    EndKey,
    PageUp,
    PageDown,
    /// Function keys (F1, etc.) T holds the index
    Function(T),
    /// Any other type of character
    OtherKey(T),
}

impl EditorKey<char> {
    pub fn unwrap(self) -> char {
        match self {
            self::OtherKey(val) => val,
            _ => panic!("called `EditorKey::unwrap()` on a `None` value"),
        }
    }
}

impl Default for Editor {
    fn default() -> Self {
        Editor {
            cursor_x: 0,
            cursor_y: 0,
            render_x: 0,
            col_offset: 0,
            row_offset: 0,
            screen_cols: 0,
            screen_rows: 0,
            rows: vec![],
            dirty: 0,
            filename: String::new(),
            status_message: String::new(),
            status_message_time: Instant::now(),
            output_buffer: String::new(),
            quit_times: KILO_QUIT_TIMES,
        }
    }
}

impl Editor {
    // ------------------------------------------------------------------------
    // Init
    // ------------------------------------------------------------------------

    pub fn new() -> Self {
        let mut instance = Self::default();

        let size = instance.get_window_size();

        instance.screen_cols = size.cols as usize;
        instance.screen_rows = (size.rows - 2) as usize;

        instance
    }

    // ------------------------------------------------------------------------
    // Terminal
    // ------------------------------------------------------------------------

    fn read_key(&mut self) -> Option<EditorKey<char>> {
        /*
            TODO: Read 1 byte by default, and read additional bytes
            if the first byte is an escape character, to resolve the
            unintentional input throttling
        */
        let stdin = io::stdin();
        let stdin = stdin.lock();
        let mut in_str = String::new();
        let mut buffer = BufReader::with_capacity(4, stdin);
        buffer.read_to_string(&mut in_str).unwrap();

        let mut input: Vec<EditorKey<char>> = vec![];

        for char in in_str.chars() {
            input.push(match char {
                '\x08' => Backspace,
                '\x7f' => Backspace,
                '\x1b' => Escape,
                '\r' => Enter,
                _ => OtherKey(char),
            });
        }

        if input.is_empty() {
            return None;
        }

        if input[0].eq(&Escape) {
            match input.len() {
                5 => {
                    // Escape code of the form `^[[NM~`
                    if input[4].eq(&OtherKey('~')) {
                        let action = match (input[2].unwrap(), input[3].unwrap()) {
                            ('1', '5') => Function('5'),
                            ('1', '7') => Function('6'),
                            ('1', '8') => Function('7'),
                            ('1', '9') => Function('8'),
                            ('2', '0') => Function('9'),
                            ('2', '1') => Function('X'), // F10
                            ('2', '4') => Function('T'), // F12
                            _ => Escape,
                        };

                        return Some(action);
                    }
                }
                4 => {
                    // Escape code of the form `^[[N~`
                    if input[3].eq(&OtherKey('~')) {
                        let action = match input[2].unwrap() {
                            '1' => HomeKey,
                            '3' => DeleteKey,
                            '4' => EndKey,
                            '5' => PageUp,
                            '6' => PageDown,
                            '7' => HomeKey,
                            '8' => EndKey,
                            _ => input[2], // Escape,
                        };

                        return Some(action);
                    }
                }
                3 => {
                    match input[1] {
                        // Escape code of the form `^[[X`
                        OtherKey('[') => {
                            let action = match input[2].unwrap() {
                                'A' => ArrowUp,
                                'B' => ArrowDown,
                                'C' => ArrowRight,
                                'D' => ArrowLeft,
                                'H' => HomeKey,
                                'F' => EndKey,

                                // Eh, just return escape otherwise
                                _ => input[2], //Escape,
                            };

                            return Some(action);
                        }
                        // Escape code of the form `^[OX`
                        OtherKey('O') => {
                            let action = match input[2].unwrap() {
                                'H' => HomeKey,
                                'F' => EndKey,
                                'P' => Function('1'),
                                'Q' => Function('2'),
                                'R' => Function('3'),
                                'S' => Function('4'),
                                _ => input[2], //Escape,
                            };

                            return Some(action);
                        }
                        _ => return Some(input[1]),
                    }
                }
                _ => return Some(input[0]),
            }
        }

        // If the character doesn't match any escape sequences, just
        // pass that character on
        return Some(input[0]);
    }

    fn get_window_size(&mut self) -> TermSize {
        match get_term_size() {
            Some(size) => size,
            None => unimplemented!("The easy way usually works"),
        }
    }

    // ------------------------------------------------------------------------
    // Input
    // ------------------------------------------------------------------------

    fn move_cursor(&mut self, key: &EditorKey<char>) {
        let row = self.rows.get(self.cursor_y);
        match key {
            ArrowLeft => {
                if self.cursor_x != 0 {
                    // Move cursor left
                    self.cursor_x -= 1;
                } else if self.cursor_y > 0 {
                    // Move to the end of the previous line
                    self.cursor_y -= 1;
                    self.cursor_x = self.rows[self.cursor_y].chars.len();
                }
            }
            ArrowRight => {
                if row.is_some() && self.cursor_x < row.unwrap().chars.len() {
                    // Move cursor right
                    self.cursor_x += 1;
                } else if row.is_some() && self.cursor_x == row.unwrap().chars.len() {
                    // Move to start of next line
                    self.cursor_y += 1;
                    self.cursor_x = 0;
                }
            }
            ArrowUp => {
                if self.cursor_y > 0 {
                    self.cursor_y -= 1;
                }
            }
            ArrowDown => {
                if self.cursor_y < self.rows.len() {
                    self.cursor_y += 1;
                }
            }
            _ => (),
        };

        let row = self.rows.get(self.cursor_y);
        let row_len = if row.is_some() {
            row.unwrap().chars.len()
        } else {
            0
        };

        // Snap to end of line when scrolling down
        if self.cursor_x > row_len {
            self.cursor_x = row_len;
        }
    }

    /// Route user input to the appropriate handler method
    pub fn process_keypress(&mut self) -> Option<EditorKey<char>> {
        let key = self.read_key();
        if key.is_some() {
            let char = key.unwrap();

            match char {
                Backspace => self._del_or_backspace(Backspace),
                DeleteKey => self._del_or_backspace(DeleteKey),
                Enter => self.insert_new_line(),
                Escape => (),
                ArrowUp => self.move_cursor(&ArrowUp),
                ArrowDown => self.move_cursor(&ArrowDown),
                ArrowLeft => self.move_cursor(&ArrowLeft),
                ArrowRight => self.move_cursor(&ArrowRight),
                PageUp => self._page_up_or_down(PageUp),
                PageDown => self._page_up_or_down(PageDown),
                HomeKey => {
                    self.cursor_x = 0;
                }
                EndKey => {
                    if self.cursor_y < self.rows.len() {
                        self.cursor_x = self.rows[self.cursor_y].chars.len();
                    }
                }
                OtherKey(c) => {
                    if c.is_ascii_control() {
                        if c == ctrl_key('q') {
                            if self.dirty > 0 && self.quit_times > 0 {
                                self.set_status_message(&format!("WARNING!!! File has unsaved changes. Press Ctrl-Q {} more times to quit.", self.quit_times));
                                self.quit_times -= 1;
                                return Some(OtherKey('\0'));
                            }
                            print!("\x1b[2J");
                            print!("\x1b[H");
                            // Break out of the input loop
                            return None;
                        }

                        if c == ctrl_key('s') {
                            // Save success/error message handled by save method
                            match self.save() {
                                Ok(_) => (),
                                Err(_) => (),
                            }
                        }

                        if c == ctrl_key('h') {
                            self._del_or_backspace(Backspace);
                        }
                    } else {
                        self.insert_char(c);
                    }
                }
                _ => (),
            };

            self.quit_times = KILO_QUIT_TIMES;

            return key;
        }

        // Continue the main input loop
        Some(OtherKey('\0'))
    }

    fn _del_or_backspace(&mut self, key: EditorKey<char>) {
        if key == DeleteKey {
            self.move_cursor(&ArrowRight);
        }
        self.delete_char();
    }

    fn _page_up_or_down(&mut self, key: EditorKey<char>) {
        let mut times = self.screen_rows;

        // Update the cursor position
        match key {
            PageUp => {
                self.cursor_y = self.row_offset;
            }
            PageDown => {
                self.cursor_y = self.row_offset + self.screen_rows - 1;
                if self.cursor_y > self.rows.len() {
                    self.cursor_y = self.rows.len();
                }
            }
            _ => (),
        }

        // Scroll the file up or down
        while times > 1 {
            times -= 1;
            self.move_cursor(match key {
                PageUp => &ArrowUp,
                PageDown => &ArrowDown,
                _ => &OtherKey('\0'),
            })
        }
    }

    // ------------------------------------------------------------------------
    // Output
    // ------------------------------------------------------------------------

    /// Equivalent of the abAppend function
    /// in the original tutorial, just appends
    /// to the `output_buffer` String in the
    /// editor struct.
    fn append_out(&mut self, str: &str) {
        self.output_buffer.push_str(str);
    }

    fn scroll(&mut self) {
        self.render_x = 0;
        if self.cursor_y < self.rows.len() {
            self.render_x = self.row_cx_to_rx(self.cursor_y);
        }

        // Vertical scrolling
        if self.cursor_y < self.row_offset {
            self.row_offset = self.cursor_y;
        }
        if self.cursor_y >= self.row_offset + self.screen_rows {
            self.row_offset = self.cursor_y - self.screen_rows + 1;
        }

        // Horizontal scrolling
        if self.render_x < self.col_offset {
            self.col_offset = self.render_x;
        }
        if self.render_x >= self.col_offset + self.screen_cols {
            self.col_offset = self.render_x - self.screen_cols + 1;
        }
    }

    fn draw_rows(&mut self) {
        for y in 0..self.screen_rows {
            let file_row = y + self.row_offset;
            if file_row >= self.rows.len() {
                if self.rows.is_empty() && y == (self.screen_rows / 3) {
                    let mut welcome = format!(
                        "Oxidized Kilo editor -- version {}",
                        env!("CARGO_PKG_VERSION")
                    );
                    if welcome.len() > self.screen_cols {
                        welcome.truncate(self.screen_cols)
                    }

                    // Center welcome message
                    let mut padding = (self.screen_cols - welcome.len()) / 2;
                    if padding > 0 {
                        self.append_out("~");
                        padding -= 1;
                    }
                    for _ in 0..padding {
                        self.append_out(" ");
                    }

                    self.append_out(&welcome);
                } else {
                    self.append_out("~");
                }
            } else {
                let mut len = self.rows[file_row].render.len() - self.col_offset;
                if len > self.screen_cols {
                    len = self.screen_cols;
                }

                let output = self.rows[file_row].render.clone();
                // let mut output = self.rows[file_row].render.clone();
                // output.truncate(len);
                self.append_out(&output[self.col_offset..len]);
            }

            self.append_out("\x1b[K");
            self.append_out("\r\n");
        }
    }

    fn draw_status_bar(&mut self) {
        self.append_out("\x1b[7m");

        let filename = if self.filename.is_empty() {
            "[No Name]"
        } else {
            &self.filename
        };

        let modified = if self.dirty > 0 { "(modified}" } else { "" };

        let mut left_message = format!("{:.80} - {} lines {}", filename, self.rows.len(), modified);
        let right_message = format!("{}/{}", self.cursor_y + 1, self.rows.len());
        let mut len = left_message.len();
        if len > self.screen_cols {
            len = self.screen_cols;
            left_message.truncate(len);
        }
        self.append_out(&left_message);

        for x in len..self.screen_cols {
            if self.screen_cols - x == right_message.len() {
                self.append_out(&right_message);
                break;
            }
            self.append_out(" ");
        }
        self.append_out("\x1b[m");
        self.append_out("\r\n");
    }

    fn draw_message_bar(&mut self) {
        self.append_out("\x1b[K");

        let mut message = self.status_message.clone();
        let message_len = message.len();
        if message_len > self.screen_cols {
            message.truncate(self.screen_cols);
        }

        let five_seconds = Duration::from_secs(5);
        if message_len > 0 && self.status_message_time.elapsed() < five_seconds {
            self.append_out(&message);
        }
    }

    pub fn refresh_screen(&mut self) -> io::Result<()> {
        self.scroll();
        self.output_buffer.clear();

        //  Hide cursor, reposition cursor
        self.append_out("\x1b[?25l");
        self.append_out("\x1b[H");

        self.draw_rows();
        self.draw_status_bar();
        self.draw_message_bar();

        // Move cursor to state position
        let y = (self.cursor_y - self.row_offset) + 1;
        let x = (self.render_x - self.col_offset) + 1;
        let cursor_code = format!("\x1b[{y};{x}H", y = y, x = x);
        self.append_out(&cursor_code);

        // Show cursor
        self.append_out("\x1b[?25h");

        let stdout = io::stdout();
        let mut handle = stdout.lock();
        handle.write_all(&self.output_buffer.as_bytes())
    }

    /// Set the status bar message
    ///
    /// To avoid creating a macro that would just forward to
    /// the `format!` macro, this method only accepts a pre-formatted
    /// string.
    ///
    /// # Example
    ///
    /// ```no-run
    /// # use rs-kilo::editor::Editor;
    /// # let editor = Editor::new();
    /// let message = format!("{} is {}", key, status);
    /// editor.set_status_message(&message);
    /// ```
    pub fn set_status_message(&mut self, message: &str) {
        self.status_message = message.to_owned();
        self.status_message_time = Instant::now();
    }

    // ------------------------------------------------------------------------
    // Row Operations
    // ------------------------------------------------------------------------

    fn row_cx_to_rx(&mut self, index: usize) -> usize {
        let mut rx: usize = 0;
        let row = &mut self.rows[index];

        for char in row.chars.chars() {
            if char == '\t' {
                rx += (KILO_TAB_STOP - 1) - (rx % KILO_TAB_STOP);
            }
            rx += 1;
        }

        rx
    }

    fn update_row(&mut self, index: usize) {
        let row = &mut self.rows[index];
        let str = row.chars.clone();

        // Cheat at rendering tabs as spaces
        let str = str.replace('\t', "    ");
        row.render = str;
    }

    fn insert_row(&mut self, at: usize, row: &str) {
        if at > self.rows.len() {
            return;
        }

        let row = EditorRow::new(row);
        self.rows.insert(at, row);

        self.update_row(at);

        self.dirty += 1;
    }

    fn delete_row(&mut self, row_index: usize) {
        if row_index > self.rows.len() {
            return;
        }

        self.rows.remove(row_index);

        self.dirty += 1;
    }

    fn row_insert_char(&mut self, row_index: usize, char_index: usize, ch: char) {
        let mut at = char_index;
        let row = &mut self.rows[row_index];

        if at > row.chars.len() {
            at = row.chars.len();
        }

        row.chars.insert(at, ch);

        self.update_row(row_index);

        self.dirty += 1;
    }

    fn row_append_string(&mut self, row_index: usize, strng: &str) {
        let row = &mut self.rows[row_index];
        row.chars += strng;

        self.update_row(row_index);

        self.dirty += 1;
    }

    fn row_delete_char(&mut self, row_index: usize, char_index: usize) {
        let row = &mut self.rows[row_index];
        if char_index >= row.chars.len() {
            return;
        }

        row.chars.remove(char_index);
        self.update_row(row_index);

        self.dirty += 1;
    }

    // ------------------------------------------------------------------------
    // Editor Operations
    // ------------------------------------------------------------------------

    fn insert_char(&mut self, ch: char) {
        if self.cursor_y == self.rows.len() {
            self.insert_row(self.rows.len(), "");
        }

        self.row_insert_char(self.cursor_y, self.cursor_x, ch);
        self.cursor_x += 1;
    }

    fn insert_new_line(&mut self) {
        if self.cursor_x == 0 {
            self.insert_row(self.cursor_y, "");
        } else {
            let row = &mut self.rows[self.cursor_y];
            let row_chars = row.chars.clone();
            let len = row.chars.len() - self.cursor_x;

            // Truncate the old row if you aren't at the end of a line
            if self.cursor_x < row.chars.len() {
                row.chars.truncate(self.cursor_x);
            }

            let slice = &row_chars[self.cursor_x..];
            self.insert_row(self.cursor_y + 1, slice);

            self.update_row(self.cursor_y);
        }

        self.cursor_y += 1;
        self.cursor_x = 0;
    }

    fn delete_char(&mut self) {
        if self.cursor_y == self.rows.len() {
            return;
        }

        if self.cursor_x == 0 && self.cursor_y == 0 {
            return;
        }

        if self.cursor_x > 0 {
            self.row_delete_char(self.cursor_y, self.cursor_x - 1);
            self.cursor_x -= 1;
        } else {
            // When deleting the first character in the row, collapse that row into the previous one
            self.cursor_x = self.rows[self.cursor_y - 1].chars.len();
            self.row_append_string(self.cursor_y - 1, &self.rows[self.cursor_y].chars.clone());
            self.delete_row(self.cursor_y);

            self.cursor_y -= 1;
        }
    }

    // ------------------------------------------------------------------------
    // File I/O
    // ------------------------------------------------------------------------

    fn rows_to_string(&mut self) -> String {
        let mut output = String::new();

        for row in &self.rows {
            // When the file is opened, newlines are stripped
            // make sure to add them back when saving!
            let row_chars = row.chars.clone() + "\n";
            output.push_str(&row_chars)
        }

        output
    }

    /// Open a file for display
    pub fn open(&mut self, filename: &str) -> io::Result<()> {
        self.filename = filename.to_owned();
        let file = File::open(&self.filename)?;
        let buf_reader = BufReader::new(file);

        let lines = buf_reader.lines().map(|l| l.unwrap());

        for line in lines {
            self.insert_row(self.rows.len(), &line);
        }

        self.dirty = 0;

        Ok(())
    }

    fn save(&mut self) -> io::Result<()> {
        if self.filename.len() == 0 {
            return Ok(());
        }

        let mut file = File::create(&self.filename)?;
        let data = &mut self.rows_to_string();

        let res = file.write_all(data.as_bytes());

        match res {
            Ok(()) => {
                self.dirty = 0;

                self.set_status_message(&format!("{} bytes written to disk", data.len()));
            }
            Err(e) => self.set_status_message(&format!("Failed to save: {:?}", e)),
        };

        file.sync_all()?;

        Ok(())
    }
}